AIR TREATMENT SYSTEM

An air treatment system comprising an air filtration apparatus having an air filter housing (33) for receiving an air filter cartridge (34), an air processing apparatus downstream of the air filter housing (33), the air processing apparatus being fluidly connected with the air filter housing (33) by means of a duct (43), the duct (43) having at its inlet end a filter sealing arrangement (76, 78) for sealing engagement with a corresponding outlet sealing arrangement (80) of an air filter cartridge (34) mounted in the air filter housing (33), wherein the system comprises a first type air filter cartridge (34) having an outlet (70) with an outlet sealing arrangement (80) having a first configuration and a second type air filter cartridge having an outlet with an outlet sealing arrangement having a second configuration different from the first configuration, the duct (43) has, over at least part of its length proximal the inlet end, inner and outer conduits (432, 431) which define an inner flow path (436) within the inner conduit (432) and an outer flow path (437) between the inner and outer conduits (432, 431) and the filter sealing arrangement (76, 78) of the duct (43) being adapted for sealing engagement with an air filter cartridge outlet sealing arrangement according to each of the first and second configurations.